Cod is a saltwater fish, belonging to the genus Gadus, and is a widely consumed food fish globally. Species like Atlantic cod and Pacific cod are found exclusively in marine environments. These fish are prized for their mild flavor and flaky, white flesh, making them a staple in various cuisines.
Where Cod Live
Atlantic cod (Gadus morhua) inhabits the colder, deeper regions of the North Atlantic Ocean, ranging from the Barents Sea to the waters off North Carolina. They primarily reside near the ocean floor, favoring rocky slopes, ledges, and coarse sediments. These fish are typically found at depths between 30 and 500 feet.
Pacific cod (Gadus macrocephalus) is found across the North Pacific Ocean, from the Bering Sea to Southern California and westward to the Sea of Japan. Like Atlantic cod, they are bottom-dwelling species on the continental shelf and upper slopes, preferring deep waters from 100 to 500 meters. Both species undertake seasonal migrations, often linked to spawning, feeding, and environmental factors like water temperature. These movements can cover significant distances.
Understanding Saltwater and Freshwater Fish
The survival of fish in either saltwater or freshwater environments depends on their ability to regulate the balance of water and salts within their bodies, a process called osmoregulation. This balance is dictated by osmosis, the movement of water across a semi-permeable membrane.
Freshwater fish live in a hypotonic environment, meaning their bodies have a higher salt concentration than the surrounding water. Water constantly diffuses into their bodies, primarily through their gills. To counteract this influx, freshwater fish actively excrete large volumes of dilute urine and absorb salts through specialized cells in their gills.
Conversely, saltwater fish like cod live in a hypertonic environment where the surrounding water has a higher salt concentration than their internal fluids. This causes water to continuously move out of their bodies, leading to dehydration. To combat water loss, saltwater fish drink seawater and possess specialized chloride cells in their gills that actively excrete excess salt. Their kidneys produce a small amount of concentrated urine to conserve water. These distinct physiological adaptations prevent freshwater fish from surviving in saltwater and vice-versa, as their osmoregulatory systems are specifically tailored to their native environments.
Fish Sometimes Mistaken for Cod
While cod refers to the Gadus genus, other fish species are sometimes confused with true cod due to similar appearances or common names. One notable example is the burbot (Lota lota), unique as the only freshwater member of the cod family (Gadidae). Burbot are found in cold, large rivers, lakes, and reservoirs across the subarctic regions of the Northern Hemisphere. They have an elongated body, often described as a cross between a catfish and an eel, with a distinctive single barbel on their chin and a mottled pattern.
Other fish sometimes misidentified as cod include Lingcod and Black Cod. Lingcod, despite its name, belongs to the greenling family and is not a true cod. Black Cod is actually Sablefish, a rich, buttery fish from the North Pacific, and is also not a member of the cod genus. Haddock and pollock are related to cod within the Gadidae family but are distinct species.